1. Field of the Invention
The present invention relates to a display device, and more particularly to an adjustable apparatus in display devices for automatic adjusting brightness.
2. Description of the Prior Art
In the current era, the performance of consumer electronic products such as cell phones, notebooks, etc. is constantly improving, especially when it comes to display devices for consumer electronic products. For example, display devices are offering users ever clearer images and greater usability.
However, it should be noted that the usability of a display device is usually based on the variable ambient light outside the display device. If the illumination of the variable ambient light outside the display device is too high, the backlight of the display device will be too low compared with the current variable ambient light. Consequently, users will need to strain their eyes to watch the images shown on the display device. Conversely, if the illumination of the variable ambient light outside the display device is too low, the backlight of the display device will be too high compared with the current variable ambient light. However, the consequences are the same as users will again not have a positive experience watching the images shown on the display device.
In the prior art, adjustable brightness apparatuses were developed to solve the problem described above. In FIG. 1, a block diagram of the previous adjustable brightness apparatus is shown. The adjustable brightness apparatus 100 includes a light detection unit 1 and a resistance R1 connecting with the light detection unit 1 externally. The light detection unit 1 includes a photo diode D1 and an amplification circuit 10.
The amplification circuit 10 amplifies variable ambient light outside the display device detected by the photo diode D1, and produces a light source signal as a photo-induced current. The light source signal is transformed into an output voltage Vout through the resistance R1. A characteristic curve illustrating the comparison between the variable ambient light and the photo-induced current is shown in FIG. 2.
However, each component of the adjustable brightness apparatuses has its limitations. Hence, the photo-induced current produced by the light detection unit 1 has a switch point C1. When the illumination of the variable ambient light is higher than the maximum level, the photo-induced current does not continually increase and becomes saturated passing the switch point C1.
The characteristic curve in FIG. 2 is divided into a weak light mode I, a normal mode II and a highlight mode III. The weak light mode I is for when users are using the display device at a place full of dark variable ambient light. The normal mode II is for when users are using the display device at a place full of normal variable ambient light. The highlight mode III is for when users are using the display device at a place full of high variable ambient light.
In the previous embodiment, when the variable ambient light is so high that the illumination of the backlight of the display device is not enough, users cannot watch images on the display device comfortably, and the display device will waste power.